Such support jacks are used in particular to prop up the trailers of a tractor-trailer rig. These support jacks are made from rectangular tubes, placed one inside the other and able to move relative to each other, as is known for example from EP 1 104 369 B1.
Since the support jacks are usually mounted onto commercial vehicles and thereby reduce the payload, there have long been efforts to make the support jacks of the lightest possible construction. This goal would also be achieved by the use of aluminum as the material, such as is described in EP 0 380 941 A2. In the case of this support device, an outer sleeve is extruded as a single piece with its fastening plate for mounting the support device onto a vehicle. Since the rough casting is in block form, this method is confined to light metals. But support devices made of light metal have not been successful on the market, since they are costly because of the high-value material and they have proven to be prone to breakdown in operational use, due to the low material strength.
Another possibility of making lighter support jacks consists of designing the outer and inner sleeves with thinner walls. This step, furthermore, leads to distinctly more favorable manufacturing expenses. But then the support jacks have a greater vulnerability to mechanical strains.